In U.S. Pat. No. 6,127,621, Simburger describes a distributed power system where a ring bus was used to connect multiple DC-DC converters in parallel and where each DC-DC converter was connected to a solar cell or battery. The picosatellites have a distributive power system that is charged by solar cells. The distributed power system is well suited for small spacecraft. Simburger describes the electronic hardware required for measuring the current and voltage characteristics of solar cells used to power a picosatellite. When the current and voltage characteristics are to be used to measure degradation in the performance of the solar cells then accurate knowledge of the angle between solar incident rays and the plane of the solar cells is required. The solar cell on-orbit is monitored while the picosatellite is spinning and stabilized around a spin axis. However, there is no attitude control system on picosatellites. As such, the angle of solar incident is unknown and degradation in the performance can not be monitored.
Picosatellites do not have any attitude control or an attitude determination system. The picosatellite will have some rotational motion imparted upon the picosatellite during ejection from the launch vehicle. This rotational motion will remain unimpeded for the operational life of the picosatellite with only minor variation that would be caused by such factors as atmospheric drag, impact with the solar wind, interaction with the earth's magnetic field, and gravity effects. Over relatively short periods of time, these effects can be ignored. Over longer periods of time, the changes in the spin rate of the spacecraft can be measured from available data.
The picosatellite can provide available data as to measured current and voltage characteristics. Because the picosatellite does not provide means determining the sun angular solar incident, the picosatellite does not provide means for determining the performance of operational solar cells. Maintenance of high performance solar cells is required to keep a picosatellite fully operational over an expected operational life. There exists a need to monitor the performance of onboard solar cells. Yet, existing picosatellite designs do not provide attitude control necessary for determining the angular solar incidence necessary for determining expected degradation of solar cell performance. These and other disadvantages are solved or reduced using the invention.